Methods for encrypting video data are used to ensure a secure transmission of video data, thus preventing unauthorised third parties from eavesdropping on the video data. Different methods have been proposed.
On the basis of an introductory consideration of known methods for encrypting video data, Liu and König propose (“A Novel Encryption Algorithm for High Resolution Video”, Proceeding of ACM NOSSDAV'05, Stevenson, Wash., USA, June 2005, pp. 69-74) a method for encrypting video data, which they call “Puzzle method”. In this method, a video data set, also called video frame, is obscured in a first method step by partially encrypting with a key stream the video data to be encrypted, and partially linking those video data to each other by means of an exclusive-or (XOR) operation. The video data obscured in this way are subsequently divided into video data blocks. The encryption is completed by interchanging the divided video data blocks in accordance with a permutation list.
It has been shown that, after encrypting the data by means of the known method, cracking the encryption by means of differential attacks by unauthorised third parties could be possible. There is therefore a demand for improving the security against attacks on the encrypted video data.